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Introduction:
In the modern threat landscape, cybersecurity professionals rely on a core arsenal of commands and techniques to defend networks, investigate incidents, and understand attacker methodologies. Mastery of these tools across operating systems and security platforms is not just an advantage—it’s a necessity for effective defense and response.
Learning Objectives:
- Acquire practical knowledge of over 25 essential commands for Linux, Windows, and security tooling.
- Understand the context and application of these commands for real-world security operations.
- Develop the ability to quickly analyze systems, harden configurations, and investigate potential compromises.
You Should Know:
1. Network Analysis and Enumeration
Effective security begins with visibility. These commands provide a foundational understanding of your network environment and active connections.
Linux: `ss -tulnpan`
Step-by-step guide: This modern replacement for `netstat` displays all listening sockets and the processes that own them.
1. Open a terminal.
2. Type `ss -tulnpan` and press Enter.
- Analyze the output: `-t` shows TCP, `-u` shows UDP, `-l` shows listening sockets, `-n` prevents name resolution (for speed), `-p` shows process names, and `-a` shows all. This helps identify unauthorized services.
Windows: `netstat -ano | findstr LISTENING`
Step-by-step guide: This command identifies all processes listening for network connections, crucial for spotting rogue backdoors.
1. Open Command Prompt or PowerShell as Administrator.
2. Execute `netstat -ano | findstr LISTENING`.
- Note the `PID` (Process Identifier) in the last column. Use Task Manager (Details tab) or `tasklist | findstr
` to identify the associated application.
Nmap: `nmap -sV -sC -O `
Step-by-step guide: A comprehensive Nmap scan for service and OS discovery.
1. Install Nmap on your system.
- Run `nmap -sV -sC -O 192.168.1.105` (replace with your target IP).
-sV: Probes open ports to determine service/version info.-sC: Runs default Nmap scripts.-O: Enables OS detection. This provides a complete fingerprint of the target.
2. Process and Service Management
Understanding what is running on a system is critical for detecting malware and unauthorized software.
Linux: `ps aux –sort=-%mem | head`
Step-by-step guide: Displays the top processes by memory consumption, helping to identify potential resource-hogging malware or crypto-miners.
1. In a terminal, run ps aux --sort=-%mem | head.
2. The `ps aux` part shows all processes. `–sort=-%mem` sorts them by memory usage (descending). `| head` shows only the top 10 results.
Windows: `Get-Process | Sort-Object WS -Descending | Select-Object -First 10`
Step-by-step guide: The PowerShell equivalent for identifying high-memory processes.
1. Open a PowerShell window.
- Run
Get-Process | Sort-Object WS -Descending | Select-Object -First 10. - The `WS` (Working Set) column shows current memory usage. Investigate any unknown processes consuming excessive resources.
Linux: `systemctl status `
Step-by-step guide: Checks the status of a critical system service, like your SSH server or web server.
1. Run `systemctl status ssh`.
- The output shows if the service is active (running), enabled (to start on boot), and recent log entries. Use this to verify the health and configuration of essential services.
3. File System Integrity and Analysis
Attackers often leave behind or modify files. Knowing how to find and analyze these artifacts is key.
Linux: `find / -type f -perm /6000 2>/dev/null`
Step-by-step guide: Locates files with SUID/SGID bits set, which can be a common privilege escalation vector.
1. Execute find / -type f -perm /6000 2>/dev/null.
2. `-perm /6000` matches files with either the SUID (4000) or SGID (2000) bit set. `2>/dev/null` suppresses permission denied errors. Audit the list for unusual binaries.
Linux: `ls -la ` | `chmod 600 `
Step-by-step guide: Verifies and corrects file permissions, especially for sensitive files like SSH private keys.
1. Check permissions: `ls -la ~/.ssh/id_rsa`.
- If the output shows permissions are too open (e.g.,
-rw-r--r--), restrict them:chmod 600 ~/.ssh/id_rsa. This ensures only the owner can read/write the file.
Windows: `icacls “C:\Sensitive\File.txt” /reset`
Step-by-step guide: Resets the permissions on a file or folder to inherit from its parent, removing any malicious explicit permissions.
1. Open an elevated Command Prompt.
- Run
icacls "C:\Sensitive\File.txt" /reset. This is a vital step in remediating files that may have been tampered with.
4. Log Interrogation and Auditing
Logs are the cornerstone of any investigation, providing a timeline of events.
Linux: `journalctl -u –since “1 hour ago”`
Step-by-step guide: Queries the systemd journal for logs related to a specific service from the last hour.
1. To check SSH login attempts, run journalctl -u ssh --since "1 hour ago".
2. Look for entries with “Failed password” or “Accepted password” to track authentication events and potential brute-force attacks.
Linux: `grep “Failed password” /var/log/auth.log`
Step-by-step guide: A classic command to quickly identify SSH brute-force attempts.
1. Run grep "Failed password" /var/log/auth.log | head -20.
2. The output will show the source IPs of failed login attempts. This data can be used to block IPs at the firewall.
Windows (PowerShell): `Get-WinEvent -FilterHashtable @{LogName=’Security’; ID=4625}`
Step-by-step guide: Pulls all failed logon events (Event ID 4625) from the Windows Security log.
1. Run PowerShell as Administrator.
- Execute
Get-WinEvent -FilterHashtable @{LogName='Security'; ID=4625} -MaxEvents 10. This is essential for detecting account lockouts and brute-force attacks on Windows systems.
5. Cloud Security Hardening
As infrastructure moves to the cloud, securing cloud configurations is paramount.
AWS CLI: `aws iam generate-credential-report` & `aws iam get-credential-report`
Step-by-step guide: Generates and retrieves a critical report on your AWS account’s IAM users and their security settings.
1. Ensure the AWS CLI is configured with appropriate permissions.
2. Run `aws iam generate-credential-report` to create the report.
3. Run `aws iam get-credential-report –output text | base64 -d > report.csv` to download and decode it. Analyze the CSV for users with old passwords, no MFA, or active access keys.
Terraform: `terraform validate` & `terraform plan`
Step-by-step guide: Security starts with Infrastructure as Code (IaC). These commands validate syntax and preview changes before deployment.
1. In your Terraform directory, run `terraform validate` to check for syntax errors.
2. Run `terraform plan -out=tfplan` to create an execution plan. Scrutinize this plan for any unintended security group rules, overly permissive IAM policies, or public-facing resources.
6. Vulnerability Assessment and Mitigation
Proactively finding and understanding vulnerabilities is a core defensive skill.
Nuclei: `nuclei -u https://target.com -t cves/ -severity critical,high`
Step-by-step guide: Uses the Nuclei scanner to check a target for known critical and high-severity vulnerabilities.
1. Install Nuclei.
- Run
nuclei -u https://target.com -t cves/ -severity critical,high. - This command uses community-driven templates to rapidly check for thousands of known CVEs. Integrate this into pre-production pipelines.
Metasploit: `use auxiliary/scanner/http/http_version`
Step-by-step guide: A basic but effective Metasploit module to fingerprint web server software and versions.
1. Start Metasploit: `msfconsole`.
2. Load the module: `use auxiliary/scanner/http/http_version`.
3. Set the target: `set RHOSTS target.com`.
- Run the scan:
run. The results help identify outdated and potentially vulnerable software.
7. API Security Testing
With the rise of microservices, API security is a major attack surface.
cURL: `curl -H “Authorization: Bearer
Step-by-step guide: Tests an API endpoint that requires JWT authentication, a common scenario in modern apps.
1. Obtain a valid JWT token from the application.
2. Run `curl -H “Authorization: Bearer
3. This tests authorization. Try accessing other user endpoints (e.g., /v1/users/5) to test for Insecure Direct Object Reference (IDOR) vulnerabilities.
OWASP ZAP: zap-baseline.py -t https://api.target.com`zap-baseline.py -t https://api.target.com`.
Step-by-step guide: Runs a baseline scan against an API using OWASP ZAP, an industry-standard tool.
<h2 style="color: yellow;">1. Install ZAP and its command-line tools.</h2>
2. Run
3. Review the generated report for common issues like missing security headers, Cross-Site Scripting (XSS), or SQL Injection flaws in API parameters.
What Undercode Say:
- The Perimeter is Everywhere: The distinction between internal and external commands is blurring. Defenders must be as fluent in querying their own cloud APIs and container orchestration as attackers are in exploiting them.
- Automation is Non-Negotiable: Manual execution of these commands is a starting point. The true power is realized when they are scripted, integrated into CI/CD pipelines, and orchestrated to provide continuous security validation.
The modern defender’s toolkit is a blend of legacy system commands and cloud-native APIs. The core principles of visibility, control, and analysis remain constant, but the domains in which they are applied have expanded dramatically from a single server to global, ephemeral cloud infrastructures. Mastery of this arsenal, from `ss` to aws iam, is what separates a reactive technician from a proactive security architect.
Prediction:
The increasing abstraction of infrastructure through serverless and containerized platforms will shift the focus of security commands from the OS level to the orchestration and API layer. Future cybersecurity skill sets will be dominated by the ability to programmatically audit, harden, and monitor cloud control planes using infrastructure-as-code security scans and policy-as-code enforcement, making manual command-line expertise the foundation for a more automated, code-centric security posture.
🎯Let’s Practice For Free:
IT/Security Reporter URL:
Reported By: Tom Ross – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
